Simplified Program Evaluation and Review Technique (PERT)

Abstract

A simplified version of the program evaluation and review technique (PERT) for project planning is developed and tested. The simplification is to reduce the number of estimates required for activity durations from three, as in conventional PERT, to two. This is accomplished by applying the normal distribution, rather than the beta, to an activity duration. The two required duration estimates are the “most likely” and the “pessimistic.” These modifications reduce the level of effort needed to apply PERT. Simplified PERT durations are subject to errors of greater than 10% when the skewness of the actual distribution is greater than 0.28 or less than −0.48. In analyzing 12 project networks, though, the simplified PERT produced values similar to those of conventional PERT for activity and project durations and variances and project duration probabilities. Hence, when activity duration distributions are not highly skewed, results similar to those of conventional PERT can be obtained using the simpler technique. Two suggestions for future research are to survey practitioners on the usefulness of the simplified PERT and to find a fixed, skewed distribution that can approximate activity durations having long tails.